Intelligent alarms

ABSTRACT

A patient in intensive care is monitored by connecting the outputs of a plurality of sensors to a computer, where the sensors all relate to one mode of functioning such as heart beating, respiration, infusion of a liquid into the patient, etc. The sensor outputs are delivered to a computer that sounds an alarm, only if all sensors that indicate one function (e.g. heart beating) indicate dangerously low operation of that function. This avoids many false alarms caused by one sensor having a low output such as due to accidental disconnection of a wire.

BACKGROUND OF THE INVENTION

False sound alarms are one of the greatest annoyances in critical care settings, such as an ICU (intensive care unit) environment. In fact, more than 97% of sound alarms are false positive alarms. Sometimes caregivers disable the alarms, which can result in preventable fatal events. A system that minimized false alarms while sounding legitimate alarms, would be of value.

SUMMARY OF THE INVENTION

The present invention provides apparatus and methods for reducing and prioritizing alarms based on sensors that sense cardiovascular patterns, respiratory patterns, electrocardiogram patterns, pulse rate and pulse strength, oxygen saturation such as is sensed by a pulse oximeter, and arterial pressure. Sensors can include those that sense central venous pressure, pulse morphology as well as arterial pressure wave forms, end tital PCO₂ (partial pressure of CO₂), operation of a ventilator, and operation of an infusion pump. By providing a plurality of sensors that each indicates one function, the failure of one sensor can be overridden by the outputs of other sensor(s).

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is view of a patient in an ICU environment, with sensors that sense functioning related to beating of a patient's heart.

FIG. 2 is a view similar to that of FIG. 1, with sensors related to infusion.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a patient P in an intensive care environment 10, wherein the patient is coupled to several sensors that monitor the functioning of various systems of the patient's body. These sensors include heart function sensors comprising a patient heart sensor 20 whose output 22 includes electrical pulses 24 of measurable height 26 and measurable spacing 28. The output of the sensor is delivered to a first input 31 of a computer 30 which measures the height and spacing of the heart pulses. If the pulse height 26 is below a selected height or the spacing 28 has increased to more than a predetermined spacing then the computer generates a failure signal on an output 32. Another sensor 40 senses the blood pressure, indicated at 41, of the patient. A signal representing the blood pressure is delivered to computer input 42. If the signal 41 indicates failure (e.g. the difference, between systolic and diastolic pressure is less than a certain minimum), a blood pressure signal output 34 is delivered. The outputs 32, 34 delivered to part 36 of the computer results in sound alarm signal 38 only if all outputs 32, 42 indicate failure of patient heart functioning.

Another sensor 50 senses the oxygen saturation of the patient's blood and delivers a signal to computer input 51. Still another sensor 52 senses the PCO₂ (partial pressure of carbon dioxide) in the patient's blood and delivers a corresponding signal to computer input 53. A pulse oximeter can be used to sense PCO₂. If the output 51 of the sensor 50 shows at least a limited level of oxygen in the patient's blood, then this means that the heart is beating to circulate the blood through the lungs to pick up oxygen. If the output 53 of sensor 52 shows at least a predetermined minimum of carbon dioxide then this indicates that the patient's blood is circulating. The computer will not generate an emergency sound alarm so long as one of the sensors 20, 40, 50, 52 indicates that the patient's heart is beating regularly, or at least does not indicate failure.

If the patient's heart is not beating regularly, then this is a critical failure that should be rectified immediately. If the output 22 of sensor 20 shows a pulse spacing 28 greater than a predetermined limit such as less than one pulse per three second, or shows a pulse height 26 less than one-fourth of the average previous height when a nurse determined that the heart was beating appropriately, then this indicates a critical failure that should be rectified immediately. However, if the output of the blood pressure sensor 40 or the output of sensor 50 or 52 is more than a minimal level, then this indicates that the heart is beating properly, or at least is beating sufficiently that this is not a critical situation. Actually, an improper output of only one sensor such as sensor 20. indicates that one of the wires that connects to the heart rate sensor 20 has been disconnected or is not connected in a low resistance connection. Functioning of the other sensors 50, 52 indicate that the heart is beating. When the computer senses a bad output, or failure from one sensor but other sensors indicate otherwise, then the computer 30 generates a visual indication such as at 70 that the heart rate sensor 20 or the blood pressure sensor 40 or other sensors such as 50 or 52 indicate improper heart functioning then lights at 72, 74 light up. It is easier for a nurse to check these sensors which cause a light 70, 72 etc. to light up when he/she has time, than to treat a poor sensor output as an emergency that requires he/she to drop everything to concentrate on the emergency.

Another function that is commonly monitored in an ICU is patient respiration. Sensors that indicate breathing include a chest vertical expansion-contraction sensor 100, an air flow sensor 102, an oxygen saturation sensor 104 and a PCO₂ sensor 106. If any of these respiration sensors indicate respiration, then no alarm will be sounded, although a visual indication will be generated that the sensor is not functioning properly.

Another function that is commonly monitored in an ICU is proper operation of an infusion pump that infuses one to several different fluids, including a saline solution, an antimicrobial fluid, etc. For those infusions that are critical, applicant can provide sensors including a sensor 110 (FIG. 2) that detects the level of fluid in a container 112 from which the fluid in introduced into the patient. The computer 30 sounds an alarm if the level does not decrease as expected, from the initial level existing when a nurse first connected the fluid container to the infusion pump, and other sensor(s) also indicate improper infusion. Sensor 114 senses movement of liquid in an infusion tube. Sensor 116 senses the pressure of air in the infusion tube.

The visual indicators preferably indicate different levels of importance. In one example, a particular one of a plurality of sensors does not agree with the other sensors for a critical function such as heart rate, breathing, infusion, and that sensor seldom malfunctions. Then, the visual indicator 70 may be a light that flashes on and off . Other visual indicators may include the continuous display of a color such as from a steady light.

Thus, the invention provides a system for generating alarms, where the system includes a plurality of sensors that sense functioning that indicates the same general condition such as heart beating, respiration, or infusion. The system generates a sound alarm indicating that a caregiver's attention is required immediately, only if all sensors indicate a patient malfunction for the particular condition. If one or more sensors indicate proper functioning, or at least temporarily acceptable functioning, then a visual indicator is operated, but a sound alarm is not sounded.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents. 

1. Apparatus for use in an intensive care unit of a medical care facility for monitoring a patient, wherein a plurality of groups of sensors are set up in said care unit and wherein each sensor of a group monitors an aspect of a potentially critical state of a patient, with each of said sensors having an output that reaches an alarm level when it senses that a corresponding medical condition of the patient has become critical, including an alarm control that has a plurality of inputs that each is connected to one of said sensors, and said alarm control has a circuit that operates a sound alarm only when the outputs of all of said plurality of sensors reach a corresponding alarm level, said circuit operating a visual alarm when an output of at least one of said sensors reaches its alarm level.
 2. The apparatus described in claim 1 wherein: a first of said groups of sensors includes a plurality of heart function sensors that each has a failure output when it detects one of the following phenomena: patient heart rate below a selected limit; patient oxygen saturation below a selected limit; patient blood pressure below a selected limit; said alarm control operates said sound alarm only when all of said heart function sensors has a failure output.
 3. The apparatus described in claim 2 wherein: said alarm control generates a visual alarm for each of said sensors that detects failure of its corresponding phenomenon, without generating a sound alarm, when only one, but not all, of said sensors fails to detect a corresponding phenomenon.
 4. The apparatus described in claim 1 wherein: said alarm control has a recording circuit that records variations in a sensor output over a predetermined time period on the order of magnitude of a minute, and delivers an alarm output when the magnitude of variations in said time period exceeds a predetermined variation.
 5. The apparatus described in claim 1 wherein: said sensors include at least two of the following: a first infusion detector that detects the flow rate of a liquid through a tube that leads into the patient, a second infusion detector that detects the height of said liquid in a bottle that connects to the patient, and a third infusion detector that detects the back pressure at the infusion site; said alarm control sets off a sound alarm only if all of said infusion detectors detect a corresponding one of said phenomena.
 6. The apparatus described in claim 5 wherein: said alarm control has a settable part that can be set to indicate that the infusion is critical or not, and that sounds an alarm only if the alarm control has been set to indicate that the infusion is critical.
 7. The apparatus described in claim 1 wherein: a first of said groups of sensors includes breathing function sensors that each has a failure output that indicates failure to detect one of the following phenomena: patient heart beats below a predetermined magnitude or at a rate below a selected limit, using an electrocardiogram; patient blood pressure below a selected limit; pressure in a patient's artery PCO₂ (partial pressure of CO₂) is below a selected limit; said alarm control operates said sound alarm only when each of said heart functioning sensors has a failure output.
 8. The apparatus described in claim 7 wherein: said alarm control generates a visual alarm for each of said sensors that is inconsistent with the outputs of a plurality of other sensors of its corresponding phenomenon, without generating a sound alarm when only some, but not all, of said sensors fails to detect a corresponding phenomenon.
 9. A method for use in an intensive care unit of a medical care facility for monitoring a patient, including connecting each of a plurality of groups of sensors to the patient wherein each of the group senses one aspect of the functioning of a system of the patient's body and each sensor has an output that reaches a failure level when it senses that a corresponding medical condition of the patient has become critical; operating an alarm control that is capable of setting off a sound alarm and a visual alarm, connecting each of said sensors to said alarm control, and setting off said sound alarm only when the outputs of all of said plurality of sensors reach their corresponding failure level, and operating a visual alarm when an output of at least one of said sensors reaches its failure level.
 10. The method described in claim 9 wherein: a first of said groups of sensors includes heart function sensors that each has a failure output that indicates failure to detect one of the following phenomena: patient heart beat rate above a selected limit; patient blood pressure above a selected limit; patient oxygen saturation above a selected limit (pulse oximeter); patient respiratory rate above a selected limit; operating said alarm control to sound said alarm only when all of said heart functioning sensors has a failure output.
 11. The apparatus described in claim 10 including: operating said alarm control to generate a visual alarm for each of said sensors that fails to detect proper functioning of its corresponding phenomenon, without generating a sound alarm when only some, but not all, of said sensors fails to detect a corresponding phenomenon. 